The use of α-Ni(OH)2 (α-phase nickel hydroxide) as a positive active material has been investigated in order to increase the number of reaction electrons and the discharge capacity of an alkaline storage battery such as a nickel-metal hydride rechargeable battery or nickel-cadmium rechargeable battery. For stabilizing α-Ni(OH)2 in an alkaline medium, preparing Al in solid solution in an amount corresponding to 5 to 20 mol % of a Ni element in the medium has been suggested (see, for example, JP-A-2010-111522). In this case, the atomic ratio of Ni:Al is in the range of 95:5 to 80:20. Moreover, since the conductivity of Ni(OH)2 of the positive active material is low, a surface of a Ni(OH)2 particle is covered with CoOOH microparticles (see, for example, WO2006/064979A1). JP-A-2007-335154 discloses that an element such as Zn or Ca is dissolved in solid solution in nickel hydroxide, but does not disclose the operation of Zn and Ca in the positive electrode material. Further, this document describes neither the phase of Ni(OH)2, nor Al or the like in solid solution. Therefore, the technique of this document may be based on the use of β-Ni(OH)2.